Aspen Global Warming Study Suggests Grim Future

By Allen Best
The Telluride Watch
August 4, 2006

ASPEN, Colo. - A new study in Aspen paints a dramatic picture of the area's climatic future should temperatures and atmospheric pollution continue to rise.

In a better-case future, in which the growth of global emissions of greenhouse gases are slowed, Aspen temperatures are projected to rise
6 degrees by the year 2100, giving it a climate comparable to what is now found at Los Alamos, N.M., or even Glenwood Springs, Colo.

On the other hand, if the direst warnings of scientists are correct and greenhouse gases remain unchecked, temperatures could rise 14 degrees by century's end, making Aspen's average daily temperatures more like those of Salt Lake City or Boise.

Even in the better-case scenario, skiing is expected to shrink as a component of Aspen's economy. In the worst-case scenario, skiing will disappear altogether.

These and other findings were released last month by Aspen town leaders, who have been working with climate scientists and others during the last year in an effort that, by several measures, is groundbreaking.

The study was the result of Aspen's Canary Initiative, which was launched a year and a half ago by the city government. In the first part of that program, Aspen examined its own contribution to greenhouse gases. The study, released this past winter, showed that Aspen was responsible for roughly twice the per capita emissions of U.S. residents, mostly due to jet travel by visitors and the lifestyles of its well-heeled residents.

The Aspen study may be the first time that broad, continent- and region-wide computer models have been used to deduce with precision the impacts of global warming in a very local area.

Older computer models projecting impacts of global warming were so broad that they failed to even show the mountain ranges of the West. Newer models do, but remain coarse.

"There are always limitations as you go to smaller and smaller regions," says John Katzenberger, executive director of the Aspen Global Change Institute. "Colorado is particularly challenging because it has storm tracks coming from different directions, and it also has the backbone of the continent. Whether storm tracks are on the east side or west side make a lot of difference."

Because of the limitations of existing computer models in predicting climate in local areas, Aspen took the unusual step of integrating several different approaches.

"They're not precise for this small of an area," says Katzenberger. "That's why we used four methods, so we would come back at it from different angles and see if they came back with consistent messages."

The models used in the study did consistently show the same increments of warming, given certain levels of greenhouse gases. The more greenhouse gases that accumulate, the lesser the chances for skiable snow.

Concentrations of carbon dioxide, a key greenhouse gas, stood at 250 parts per million in the atmosphere 200 years ago, at the start of the Industrial Revolution. Concentrations of the gas are currently at 379 parts per million. Many scientists say that 550 parts per million is the maximum that the earth's atmosphere can absorb without catastrophic consequences. Given current trajectories, concentrations are likely to hit that number in 2050. Aspen's worst-case scenario assumes 900 parts per million by the end of the 21st century.

However, Katzenberger notes that 550 parts per million is not an inevitability. "It's possible, if the world really wanted, it could do better than that," he says. "And if it did so, the climate impacts could be greatly reduced."

Unlike future temperatures, the climate models for Aspen are unsure about future precipitation levels. Again, this mirrors the more continent-wide models from which the local predictions were teased.

"Given the current state of climate modeling, what precipitation will do in northwest America, and with Aspen in particular, is really hard to say with any degree of confidence," says Brian Lazard, a hydrologist with Stratus Consulting, a Boulder-based firm. "What we can say with a great deal of confidence is that the temperature will go up. It's just a matter of how much."

The warmer temperatures mean Aspen will see less snow and more rain. What snow it does get will melt more rapidly, up to three weeks earlier, mirroring changes that have been documented in California's Sierra Nevada over the last 50 years. In other words, the runoff seen this year and in 2002 is likely to become the norm in future years.

Dan Richardson, the global warming project manager for the City of Aspen, says he is most taken aback by the implications of earlier runoff. "It's almost so big you can't get your arms around it."

The implications have also been under scrutiny in California, where much of the annual water supply comes from the snowpack in the Sierra Nevada.

Many of the study's key findings have been previously predicted, but the study gives them a stronger, scientific foundation. They include:

• Local warming will force some plant and animal species to ascend to higher elevations. By mid-century, for example, the vegetation in Aspen is likely to look more like what is now seen near Basalt, a town that is 1,400 feet lower in elevation and 20 miles away. Species of the alpine tundra such as ptarmigan and pika will face threats of localized extinction, something called extirpation.

• Rising temperatures will increase the likelihood of insect outbreaks. Cold nights and winters help keep insect populations in check. Warmer nights and winters, along with longer, warmer summers, will increase the risk of pests to spruce-fir forest and to aspen groves. Bark beetles in pine trees are likely to be less checked.

• Existing invasive species such as Canada thistle and leafy spurge will spread, and new non-native species may invade.

• Ski season, if it remains, will occur at higher elevations, and during a shorter season. Rafting season will be shorter, and water supplies will be more stressed.

• Total precipitation has decreased 6 percent in the past 25 years, and at higher elevations of 10,600 feet, the precipitation has decreased 18 percent. In addition, the amount falling in the form of snow has decreased 18 percent.

Results of the study, says Katzenberger, should be useful to communities making decisions about how to adapt to climate changes. The economy of Aspen, says the report, is more likely adaptable to climate change than are plants and animals. But, in general, the greater the warming, the more difficult and expensive adaptation to climate change will be.

Aspen figures to use its prominence to warn about the dangers of the current and projected volume of greenhouse gas emissions. The Canary Initiative has received major play in national magazines and TV broadcasts. It is also sponsoring a conference Oct. 11-13 geared toward mountain and gateway communities.

Aspen's next step will be to compile a draft action plan, to determine what it can do better to reduce greenhouse gas emissions. Aside from its dependence on travel and its many large homes, the city and nearby Pitkin County have already taken many notable steps, among them adoption of building codes designed to maximize energy efficiency in buildings and a high reliance upon hydro and wind energy.

Informant: David Sunfellow


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